Known skis of the prior art generally comprise a narrow strip of wood, metal or the like having a tapered, front ski tip and a usually blunt rear end. They have a bottom or running surface which can be coated with a polymeric substance such as polyethylene and/or a wax to improve the sliding and other properties of the skis.
Bindings for holding or mounting the foot or footwear such as a boot are provided on the upper surface of a ski in the middle region of the length of the ski.
A variety of techniques have been used to improve the sliding, pushing and climbing properties of the running surface of skis.
Good sliding properties as well as the ability to climb and push are required particularly of a cross country ski. These properties can be attained by waxing the middle of the running surface of the ski by hard wax and/or other dabbing waxes e.g. klister wax.
It is also known to form a climbing aid by providing contours in the running surface which grip the snow track unidirectionally. This climbing aid may be located in the ski's center region and the formation can have a scale-like shape, a prong-like shape, or a step-like form.
These shapes are impressed or embossed in the polyethylene coating on the running surface.
The disadvantage of waxed skis where the wax forms the climbing aid, is that either the sliding properties of an optimally waxed cross country ski or the climbing properties of an optimally waxed ski can be optimized but not both. The climbing and sliding properties of the cross country ski with this climbing aid are always inferior to the optimum possible therefore, since there is always a trade-off between these two properties.
A disadvantage of mechanical (contoured) climbing aids is that mere surface abrasion is enough to reduce or eliminate the effectiveness of the contours and frequently use of skis with such contours generates a considerable amount of noise.
A coating for the running surface of a ski comprising a mixture of an elastomer and hard fiber component is also known as a climbing aid. The fibers are designed to project partially from the elastomer matrix and engage or grip the snow. The disadvantage of this climbing aid is that the fiber components are tend to ice up under various snow and temperature conditions.
German Patent document DE-OS Pat. No. 30 03 503 proposes the flame treatment with a gas flame of the plastic material on the ski bottom or running surface in the middle region of the ski to increase the adhesion between the snow and the ski in this region.
The flame treatment of the plastic material is, however, problematical particularly because of nonreproducibility and the unpredictability of the result.
The result depends on the duration and intensity of the flaming, so that variations in quality can scarcely be avoided. The heating or flaming may affect only a very thin layer of the polyethylene upper surface, so that by natural abrasion, the polyethylene upper surface after long use is worn off or fouled up and the layer then no longer will have an increased friction coefficient.